Known in the art are a variety of room temperature-vulcanizable (RTV) silicone rubber compositions which cure into rubbery elastomers at room temperature. Rubbers resulting from such RTV compositions have improved weather resistance, durability, heat resistance and freeze resistance as compared with other organic rubbers and are thus used in a wide variety of fields. Especially in the building field, RTV compositions are often used for the bonding of glass plates, the bonding of metal and glass, the sealing of concrete joints and the like. Recently, RTV compositions newly find wide use as coating material for buildings, plants, water conduits (inclusive of inner and outer surfaces) and the like.
The organopolysiloxane on which RTV is based, however, has the nature of electrostatic charging and is thus likely to adsorb dust in air. This is problematic in that surfaces of cured sealing or coating materials are markedly fouled with the lapse of time, losing aesthetic appearance. One typical solution to this problem is by adding or incorporating surfactants having a polyoxyethylene group, sorbitan residue or disaccharide residue to RTV (see JP-A 56-76452 and JP-A 56-76453). To achieve fully satisfactory results by the above method, the surfactants must be added in large amounts, undesirably degrading the adhesion which is one important function of RTV sealing or coating materials.
Once underwater structures are installed or in service, aquatic organisms living in waters like sea and rivers such as barnacle, lamp chimney, serpula, mussel, Bryozoa, and seaweeds (e.g., Enteromorpha and Ulva) deposit and grow on splashed and submerged surface areas, causing various damages. In the case of a ship, for example, the deposition of organisms to the hull increases frictional resistance to water to reduce the speed. The fuel consumption must be increased to maintain a certain speed, which is uneconomical. If organisms deposit on structures of a harbor facility which are fixed at or below the water surface, it becomes difficult for the structures to exert their own function and sometimes, their substrates can be eroded. If organisms deposit on fish culture nets or fixed shore nets, net openings are clogged, eventually leading to the death of fishes.
Conventional means for preventing deposition and growth of aquatic organisms on underwater structures is the application to such structures of anti-fouling or fouling release paints having incorporated therein toxic anti-fouling or fouling release agents such as organotin compounds and cuprous oxide. Although such anti-fouling paints are effective for substantially preventing deposition and growth of aquatic organisms, the use of toxic anti-fouling or fouling release agents is harmful to the environmental safety and hygiene during preparation and application of paints. Additionally, the toxic anti-fouling or fouling release agent is slowly leached out of the coating in water, with the risk of contaminating the surrounding water area over a long term. For this reason, the use of toxic anti-fouling or fouling release agents was legally banned.
There have been proposed paint compositions which are effective for preventing deposition and growth of aquatic organisms, but free of toxic anti-fouling or fouling release agents. Paint compositions which are designed to impart anti-fouling or fouling release property by reducing the surface tension of coatings include non-toxic anti-fouling or fouling release paint compositions comprising RTV and liquid paraffin or petrolatum (see JP-A 58-13673 and JP-A 62-84166). Japanese Patent Nos. 2,503,986 and 2,952,375 disclose non-toxic anti-fouling or fouling release paint compositions comprising a reaction curing silicone resin and a less compatible, non-reactive, polar group-containing silicone resin wherein under the impetus of volume shrinkage associated with curing of the reaction curing silicone resin, the polar group-containing silicone resin bleeds out of the surface, which cooperates with the low surface tension of reaction curing silicone resin, to exhibit anti-fouling or fouling release property. These non-toxic anti-fouling or fouling release paint compositions, however, suffer from environmental safety and hygiene problems because the less compatible, non-reactive, polar group-containing silicone resin serving as bleed oil is a polyoxyethylene group-containing silicone resin in which ethylene oxide or propylene oxide is added to a silicon atom via a C—C bond or a silicone resin having an alkoxy group bonded to a silicon atom at a molecular end via an ethylene oxide or propylene oxide group.